1. Follow the above DGuitar link, and download DGuitar-0.5.8.zip from one of the mirror sites.
2. Unzip the file (on WindowsXP, just double click and drag out the whole DGuitar-0.5.8 folder)
3. Go into the unzipped DGuitar-0.5.8 folder and click on DGuitar.bat
4. Top left, go to "Program" and then "Open" (GP4), and find the JerryC_Canon_Rock.gp4 file.